Adding an Additional System

[Graham W]

Hello,

We had a 4kW system installed 12 months ago and would like to install an additional 4kw system on our attached garage.

As we only have 1 supply and 1 meter would this be allowed by National grid and would a second system effect the tariif rate of the existing system.

Thanks,

Graham

 

[SolarCity]

Permission would need to be obtained from the DNO to connect anything above 16A which is 3.68kWp. As you are already above this mark then they will need to be contacted. The installer could sort this out.

 

[FB.]

As we only have 1 supply and 1 meter would this be allowed by National grid

Maybe. The District Network Operator would need to approve it in writing before you can go ahead. They will look at the ability of the local grid to handle the two-way power fluctuation, and also look at other solar arrays nearby which may already be putting a strain on the grid's ability to cope with the reverse power flows.

would a second system effect the tariif rate of the existing system

A second array would be paid at the applicable rate (probably the 4-10kW band, which is somewhere around 14p FiT and 0.5x4.5p export). It MUST have the EPC-D certificate BEFORE any work starts on the array; it cannot be EPC'd afterwards, unlike what seems to be the case for many domestic sub-4kW installations during 2012.
The second array will probably have the same FiT license number, but have a separate generation meter.
It should not affect your existing array's FiT rate.

Here is a comment from Scottish Power, in response to a query I made:

"...Thank you for your email.

In response to your query, your original installation will retain its current tariff and 25 year period.

The additional panels would be paid at the rate for the higher capacity range of 4kW-10kW, currently 14.5p per kWh for a 20 year period, with the eligibility date for the new array being its commissioning date. Both payment periods would run in parallel.

Please be aware there is a rate change on 1 November 2012 whereby the rate will reduce to 13.99p per kWh.

Yes, you would require to submit two readings, one for each of the meters.

Should you proceed with the installation and wish to apply for the Feed In Tariff for the additional panels, you will need to complete a separate application form and send it in to us, together with a copy of the MCS Certificate and Energy Performance Certificate......"

 

[SolarRoofSols]

Solarcity is correct, you will have to apply to the DNO for approval. The FIT rate of your existing shouldn't be affected but the new installation will only be eligible for the current rate.

When I enquired about adding to a customer's system I was told that both systems would be hooked up to the same generation meter and your FIT provider would take the 1 reading and proportionately allocate the FIT payment to based on the installation sizes, but I would check with your FIT provider as to how they would want to do this - or get your installer to.

 

[FB.]

Here are links to some topics I started, asking the kind of questions that you'll be asking - and from which some of my above reply was derived:

http://www.electriciansforums.net/p...rum/63366-if-i-added-second-3-4kwp-array.html

http://www.electriciansforums.net/p...green-energy-forum/63056-what-my-chances.html

http://www.electriciansforums.net/p...203-second-pv-array-requires-three-phase.html

.

 

[FB.]

When I enquired about adding to a customer's system I was told that both systems would be hooked up to the same generation meter and your FIT provider would take the 1 reading and proportionately allocate the FIT payment to based on the installation sizes

Interesting. Scottish Power said a separate generation meter.
Perhaps they meant a new array would have an additional, separate generation meter, while an extension to an existing array using the same inverter (say from 12 panels <3.0kWp> to 14 panels <3.5kWp>) would have the pro-rata adjustment for the different FiT rate at the time of the extension.

 

[steve Leese]

I think you will find you will have to put the two system through a G59 relay, as the rules on domestic multi installations change last march. Scottish power made us put a G59 relay in for the two systems comprising of 3.4kw and 2.4 kw, this put an extra cost of £2,900 plus vat on the bill, lucky the customer is a wealthy eco worrior

 

[Graham W]

Thanks for the replies and information.

Although we have 4KW of panels the inverter we have is a power1 and is capped at 16A, I believe that this is a common set-up.

Can anyone confirm if the G59 relay as suggested above is definetely required as this additional cost would make the project unaffordable for us.


Thanks again.

 

[BruceB]

Can anyone confirm if the G59 relay as suggested above is definetely required as this additional cost would make the project unaffordable for us.

Regret we cannot give that answer here. It is up to the DNO. They may be happy with inverters on G83 settings, or require a single G59 relay, or be content with both inverters set to G59 rather than G83, if the inverters are adjustable.

 

[Worcester]

The only one that can confirm is the DNO when you submit your application, thre are too many factors.

If you are dealing with an installation near Cheltenham - just pick up the phone and speak to WPD they are very helpful.

 

[SolarCity]

I'd be very surprised if you'd be asked for a G59 relay. As the system size is still relatively small then most DNOs should accept inverters set to G59 parameters.

 

[steve Leese]

Let me clarify what the DNO said me about the systems we fitted,the 3.4kw was set at G83 and running no problem, when i wanted fit the 2.4kw system i rang the DNO, they said they would not let me fit another system under G83 as the total load would be over 16A they insisted it was done with a G59 relay. i wanted to reset the sma inverters to G59 but they were having none of it, and i was told not to alter the original inverter either. I wonder if it might just be who you are dealing with at the time. It might be that different DNOs have other ideas on this matter but i can only go on past experience. Once the relay and 2.4kw system was fitted and tested everything was fine with the DNO, just a costly excersize.

 

[Graham W]

I have contacted WPD who were very helpful. The existing inverter would need to be switched to G59 settings, the second inverter would also have to be set to G59 settings or a single, larger G59 inverter could be used for both sets of panels. No mention of a G59 relay. They have also said that the transformer would need to be upgraded to accept the increased voltage and that this would costs around £5000, possibly more if the cable also needs to be upgraded.

The additional costs make the project unviable for us.

Thank you all for your advice, comments and suggestions.

Regards,

Graham

 

[steve Leese]

Sorry to hear you may not get the job but that is the DNO for you. the thing is if you were installing the other 4kw near by and kept it to 16A it could of still gone through the same trany without informing them at all, untill after it was done, seems daft to me.

 

[Worcester]

At least the DNO took the sensible option of allowing the inverters to be configured to G59 (as they are type approved for that) shame about the network upgrade costs.